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fix bug with max_values in union! #30315

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Dec 11, 2018
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fix bug with max_values in union! #30315

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6 changes: 4 additions & 2 deletions base/abstractset.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -69,9 +69,11 @@ function union!(s::AbstractSet, sets...)
end

max_values(::Type) = typemax(Int)
max_values(T::Type{<:Union{Nothing,BitIntegerSmall}}) = 1 << (8*sizeof(T))
max_values(T::Union) = max(max_values(T.a), max_values(T.b))
max_values(T::Union{map(X -> Type{X}, BitIntegerSmall_types)...}) = 1 << (8*sizeof(T))
# saturated addition to prevent overflow with typemax(Int)
max_values(T::Union) = max(max_values(T.a), max_values(T.b), max_values(T.a) + max_values(T.b))
max_values(::Type{Bool}) = 2
max_values(::Type{Nothing}) = 1
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Could this be applied to all singleton types? You can check whether a type is a singleton using isdefined(T, :instance) (there's an issingletontype helper function for this in replace.jl).

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Yes seems like a good idea!
As CI is green and I think this is an urgent fix to have, I will merge as-is later today and implement your idea (which is not directly related to the bugfix) separately.


function union!(s::AbstractSet{T}, itr) where T
haslength(itr) && sizehint!(s, length(s) + length(itr))
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21 changes: 21 additions & 0 deletions test/sets.jl
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Expand Up @@ -628,6 +628,27 @@ end
end
end

@testset "optimized union! with max_values" begin
# issue #30315
T = Union{Nothing, Bool}
@test Base.max_values(T) == 3
d = Set{T}()
union!(d, (nothing, true, false))
@test length(d) == 3
@test d == Set((nothing, true, false))
@test nothing in d
@test true in d
@test false in d

for X = (Int8, Int16, Int32, Int64)
@test Base.max_values(Union{Nothing, X}) == (sizeof(X) < sizeof(Int) ?
2^(8*sizeof(X)) + 1 :
typemax(Int))
end
# this does not account for non-empty intersections of the unioned types
@test Base.max_values(Union{Int8,Int16}) == 2^8 + 2^16
end

struct OpenInterval{T}
lower::T
upper::T
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